Should I do my first water change?

[Swifty3565]

My tank has been cycling for 19 days.  Current parameter are; ph 8.0, ammonia 0ppm, nitrites 0ppm, nitrates 40ppm.  My ammonia peaked at 0.25ppm on day 15, and my nitrates have been at 40ppm since day 16.  Is it time to do a large water change?  If so can I slowly begin adding livestock after the water change?

[Clown79]

How did you cycle the tank?

[Swifty3565]

I cycled with arag-alive sand, 27lbs of live rock.  Lights on for 10 hours a day. No fish.

[Clown79]

Cycles usually are quicker with liverock use, especially if the rock was in a good clean condition.

 

We're you testing from day one? I'm just trying to clarify the ammonia peaking on day 15? 

 

If you saw ammonia rise and drop, nitrite rise and drop, that's usually the end of cycling.

 

You can do a waterchange but I would still monitor before adding anything and then I would go slow on any additions

[Swifty3565]

I have been monitoring since day 7.  I have seen ammonia rise and drop, however nitrite has been at 0 since I began testing. Ammonia topped out at 0.25ppm on day 15 and was back to zero on day 16 and has stayed at 0.  

 

My intention is to do a 50% water change and then monitor for a few more days.  Hope to introduce the first fish late next week.  Is this a reasonable plan?

 

 

9 hours ago, Clown79 said:

How did you cycle the tank?

 

[Clown79]

Hmm. That's odd that nitrite never increased.

Not sure If it's because you started testing 7 days in, it all may have processed quickly.

 

Maybe @brandon429 or @seabass can add their take on this situation?

[seabass]

Different bacteria process ammonia versus nitrite. It's possible that the nitrite oxidizing bacteria were able to keep up while the ammonia oxidizing bacteria couldn't.  We know that the nitrite oxidizing bacteria are present and working because we see the resulting nitrate.  While we often see a nitrite spike follow an ammonia spike, it's not required.

 

Yes, your tank is ready for a water change.  At 40 ppm, you would need to do a 75% water change to bring nitrate down to 10 ppm (and ready for livestock).

[Swifty3565]

Thanks for the help seabass and clown79.  I guess tomorrow will be water change day then.  I will shoot for about a 15 gallon change.  It's a bc32 and with the 27 lbs of rock I'm thinking  that should be in the ball park of 75%, or should I do more?

[seabass]

You can change more if you want (it won't hurt anything if you do).  But if you bring nitrate down to 10 ppm, that should be enough.